Entries Tagged "Microsoft"

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The FBI Is Now Securing Networks Without Their Owners’ Permission

In January, we learned about a Chinese espionage campaign that exploited four zero-days in Microsoft Exchange. One of the characteristics of the campaign, in the later days when the Chinese probably realized that the vulnerabilities would soon be fixed, was to install a web shell in compromised networks that would give them subsequent remote access. Even if the vulnerabilities were patched, the shell would remain until the network operators removed it.

Now, months later, many of those shells are still in place. And they’re being used by criminal hackers as well.

On Tuesday, the FBI announced that it successfully received a court order to remove “hundreds” of these web shells from networks in the US.

This is nothing short of extraordinary, and I can think of no real-world parallel. It’s kind of like if a criminal organization infiltrated a door-lock company and surreptitiously added a master passkey feature, and then customers bought and installed those locks. And then if the FBI got a court order to fix all the locks to remove the master passkey capability. And it’s kind of not like that. In any case, it’s not what we normally think of when we think of a warrant. The links above have details, but I would like a legal scholar to weigh in on the implications of this.

Posted on April 14, 2021 at 9:56 AMView Comments

More on the Chinese Zero-Day Microsoft Exchange Hack

Nick Weaver has an excellent post on the Microsoft Exchange hack:

The investigative journalist Brian Krebs has produced a handy timeline of events and a few things stand out from the chronology. The attacker was first detected by one group on Jan. 5 and another on Jan. 6, and Microsoft acknowledged the problem immediately. During this time the attacker appeared to be relatively subtle, exploiting particular targets (although we generally lack insight into who was targeted). Microsoft determined on Feb. 18 that it would patch these vulnerabilities on the March 9th “Patch Tuesday” release of fixes.

Somehow, the threat actor either knew that the exploits would soon become worthless or simply guessed that they would. So, in late February, the attacker changed strategy. Instead of simply exploiting targeted Exchange servers, the attackers stepped up their pace considerably by targeting tens of thousands of servers to install the web shell, an exploit that allows attackers to have remote access to a system. Microsoft then released the patch with very little warning on Mar. 2, at which point the attacker simply sought to compromise almost every vulnerable Exchange server on the Internet. The result? Virtually every vulnerable mail server received the web shell as a backdoor for further exploitation, making the patch effectively useless against the Chinese attackers; almost all of the vulnerable systems were exploited before they were patched.

This is a rational strategy for any actor who doesn’t care about consequences. When a zero-day is confidential and undiscovered, the attacker tries to be careful, only using it on attackers of sufficient value. But if the attacker knows or has reason to believe their vulnerabilities may be patched, they will increase the pace of exploits and, once a patch is released, there is no reason to not try to exploit everything possible.

We know that Microsoft shares advance information about updates with some organizations. I have long believed that they give the NSA a few weeks’ notice to do basically what the Chinese did: use the exploit widely, because you don’t have to worry about losing the capability.

Estimates on the number of affected networks continues to rise. At least 30,000 in the US, and 100,000 worldwide. More?

And the vulnerabilities:

The Chinese actors were not using a single vulnerability but actually a sequence of four “zero-day” exploits. The first allowed an unauthorized user to basically tell the server “let me in, I’m the server” by tricking the server into contacting itself. After the unauthorized user gained entry, the hacker could use the second vulnerability, which used a malformed voicemail that, when interpreted by the server, allowed them to execute arbitrary commands. Two further vulnerabilities allow the attacker to write new files, which is a common primitive that attackers use to increase their access: An attacker uses a vulnerability to write a file and then uses the arbitrary command execution vulnerability to execute that file.

Using this access, the attackers could read anybody’s email or indeed take over the mail server completely. Critically, they would almost always do more, introducing a “web shell,” a program that would enable further remote exploitation even if the vulnerabilities are patched.

The details of that web shell matter. If it was sophisticated, it implies that the Chinese hackers were planning on installing it from the beginning of the operation. If it’s kind of slapdash, it implies a last-minute addition when they realized their exploit window was closing.

Now comes the criminal attacks. Any unpatched network is still vulnerable, and we know from history that lots of networks will remain vulnerable for a long time. Expect the ransomware gangs to weaponize this attack within days.

EDITED TO ADD (3/12): Right on schedule, criminal hacker groups are exploiting the vulnerabilities.

EDITED TO ADD (3/13): And now the ransomware.

Posted on March 10, 2021 at 6:28 AMView Comments

Chinese Hackers Stole an NSA Windows Exploit in 2014

Check Point has evidence that (probably government affiliated) Chinese hackers stole and cloned an NSA Windows hacking tool years before (probably government affiliated) Russian hackers stole and then published the same tool. Here’s the timeline:

The timeline basically seems to be, according to Check Point:

  • 2013: NSA’s Equation Group developed a set of exploits including one called EpMe that elevates one’s privileges on a vulnerable Windows system to system-administrator level, granting full control. This allows someone with a foothold on a machine to commandeer the whole box.
  • 2014-2015: China’s hacking team code-named APT31, aka Zirconium, developed Jian by, one way or another, cloning EpMe.
  • Early 2017: The Equation Group’s tools were teased and then leaked online by a team calling itself the Shadow Brokers. Around that time, Microsoft cancelled its February Patch Tuesday, identified the vulnerability exploited by EpMe (CVE-2017-0005), and fixed it in a bumper March update. Interestingly enough, Lockheed Martin was credited as alerting Microsoft to the flaw, suggesting it was perhaps used against an American target.
  • Mid 2017: Microsoft quietly fixed the vulnerability exploited by the leaked EpMo exploit.

Lots of news articles about this.

Posted on March 4, 2021 at 6:25 AMView Comments

Twelve-Year-Old Vulnerability Found in Windows Defender

Researchers found, and Microsoft has patched, a vulnerability in Windows Defender that has been around for twelve years. There is no evidence that anyone has used the vulnerability during that time.

The flaw, discovered by researchers at the security firm SentinelOne, showed up in a driver that Windows Defender — renamed Microsoft Defender last year — uses to delete the invasive files and infrastructure that malware can create. When the driver removes a malicious file, it replaces it with a new, benign one as a sort of placeholder during remediation. But the researchers discovered that the system doesn’t specifically verify that new file. As a result, an attacker could insert strategic system links that direct the driver to overwrite the wrong file or even run malicious code.

It isn’t unusual that vulnerabilities lie around for this long. They can’t be fixed until someone finds them, and people aren’t always looking.

Posted on February 24, 2021 at 6:19 AMView Comments

SVR Attacks on Microsoft 365

FireEye is reporting the current known tactics that the SVR used to compromise Microsoft 365 cloud data as part of its SolarWinds operation:

Mandiant has observed UNC2452 and other threat actors moving laterally to the Microsoft 365 cloud using a combination of four primary techniques:

  • Steal the Active Directory Federation Services (AD FS) token-signing certificate and use it to forge tokens for arbitrary users (sometimes described as Golden SAML). This would allow the attacker to authenticate into a federated resource provider (such as Microsoft 365) as any user, without the need for that user’s password or their corresponding multi-factor authentication (MFA) mechanism.
  • Modify or add trusted domains in Azure AD to add a new federated Identity Provider (IdP) that the attacker controls. This would allow the attacker to forge tokens for arbitrary users and has been described as an Azure AD backdoor.
  • Compromise the credentials of on-premises user accounts that are synchronized to Microsoft 365 that have high privileged directory roles, such as Global Administrator or Application Administrator.
  • Backdoor an existing Microsoft 365 application by adding a new application or service principal credential in order to use the legitimate permissions assigned to the application, such as the ability to read email, send email as an arbitrary user, access user calendars, etc.

Lots of details here, including information on remediation and hardening.

The more we learn about the this operation, the more sophisticated it becomes.

In related news, MalwareBytes was also targeted.

Posted on January 21, 2021 at 6:31 AMView Comments

US Cyber Command and Microsoft Are Both Disrupting TrickBot

Earlier this month, we learned that someone is disrupting the TrickBot botnet network.

Over the past 10 days, someone has been launching a series of coordinated attacks designed to disrupt Trickbot, an enormous collection of more than two million malware-infected Windows PCs that are constantly being harvested for financial data and are often used as the entry point for deploying ransomware within compromised organizations.

On Sept. 22, someone pushed out a new configuration file to Windows computers currently infected with Trickbot. The crooks running the Trickbot botnet typically use these config files to pass new instructions to their fleet of infected PCs, such as the Internet address where hacked systems should download new updates to the malware.

But the new configuration file pushed on Sept. 22 told all systems infected with Trickbot that their new malware control server had the address, which is a “localhost” address that is not reachable over the public Internet, according to an analysis by cyber intelligence firm Intel 471.

A few days ago, the Washington Post reported that it’s the work of US Cyber Command:

U.S. Cyber Command’s campaign against the Trickbot botnet, an army of at least 1 million hijacked computers run by Russian-speaking criminals, is not expected to permanently dismantle the network, said four U.S. officials, who spoke on the condition of anonymity because of the matter’s sensitivity. But it is one way to distract them at least for a while as they seek to restore operations.

The network is controlled by “Russian speaking criminals,” and the fear is that it will be used to disrupt the US election next month.

The effort is part of what Gen. Paul Nakasone, the head of Cyber Command, calls “persistent engagement,” or the imposition of cumulative costs on an adversary by keeping them constantly engaged. And that is a key feature of CyberCom’s activities to help protect the election against foreign threats, officials said.

Here’s General Nakasone talking about persistent engagement.

Microsoft is also disrupting Trickbot:

We disrupted Trickbot through a court order we obtained as well as technical action we executed in partnership with telecommunications providers around the world. We have now cut off key infrastructure so those operating Trickbot will no longer be able to initiate new infections or activate ransomware already dropped into computer systems.


We took today’s action after the United States District Court for the Eastern District of Virginia granted our request for a court order to halt Trickbot’s operations.

During the investigation that underpinned our case, we were able to identify operational details including the infrastructure Trickbot used to communicate with and control victim computers, the way infected computers talk with each other, and Trickbot’s mechanisms to evade detection and attempts to disrupt its operation. As we observed the infected computers connect to and receive instructions from command and control servers, we were able to identify the precise IP addresses of those servers. With this evidence, the court granted approval for Microsoft and our partners to disable the IP addresses, render the content stored on the command and control servers inaccessible, suspend all services to the botnet operators, and block any effort by the Trickbot operators to purchase or lease additional servers.

To execute this action, Microsoft formed an international group of industry and telecommunications providers. Our Digital Crimes Unit (DCU) led investigation efforts including detection, analysis, telemetry, and reverse engineering, with additional data and insights to strengthen our legal case from a global network of partners including FS-ISAC, ESET, Lumen’s Black Lotus Labs, NTT and Symantec, a division of Broadcom, in addition to our Microsoft Defender team. Further action to remediate victims will be supported by internet service providers (ISPs) and computer emergency readiness teams (CERTs) around the world.

This action also represents a new legal approach that our DCU is using for the first time. Our case includes copyright claims against Trickbot’s malicious use of our software code. This approach is an important development in our efforts to stop the spread of malware, allowing us to take civil action to protect customers in the large number of countries around the world that have these laws in place.

Brian Krebs comments:

In legal filings, Microsoft argued that Trickbot irreparably harms the company “by damaging its reputation, brands, and customer goodwill. Defendants physically alter and corrupt Microsoft products such as the Microsoft Windows products. Once infected, altered and controlled by Trickbot, the Windows operating system ceases to operate normally and becomes tools for Defendants to conduct their theft.”

This is a novel use of trademark law.

Posted on October 15, 2020 at 6:01 AMView Comments

Vulnerability Finding Using Machine Learning

Microsoft is training a machine-learning system to find software bugs:

At Microsoft, 47,000 developers generate nearly 30 thousand bugs a month. These items get stored across over 100 AzureDevOps and GitHub repositories. To better label and prioritize bugs at that scale, we couldn’t just apply more people to the problem. However, large volumes of semi-curated data are perfect for machine learning. Since 2001 Microsoft has collected 13 million work items and bugs. We used that data to develop a process and machine learning model that correctly distinguishes between security and non-security bugs 99 percent of the time and accurately identifies the critical, high priority security bugs, 97 percent of the time.

News article.

I wrote about this in 2018:

The problem of finding software vulnerabilities seems well-suited for ML systems. Going through code line by line is just the sort of tedious problem that computers excel at, if we can only teach them what a vulnerability looks like. There are challenges with that, of course, but there is already a healthy amount of academic literature on the topic — and research is continuing. There’s every reason to expect ML systems to get better at this as time goes on, and some reason to expect them to eventually become very good at it.

Finding vulnerabilities can benefit both attackers and defenders, but it’s not a fair fight. When an attacker’s ML system finds a vulnerability in software, the attacker can use it to compromise systems. When a defender’s ML system finds the same vulnerability, he or she can try to patch the system or program network defenses to watch for and block code that tries to exploit it.

But when the same system is in the hands of a software developer who uses it to find the vulnerability before the software is ever released, the developer fixes it so it can never be used in the first place. The ML system will probably be part of his or her software design tools and will automatically find and fix vulnerabilities while the code is still in development.

Fast-forward a decade or so into the future. We might say to each other, “Remember those years when software vulnerabilities were a thing, before ML vulnerability finders were built into every compiler and fixed them before the software was ever released? Wow, those were crazy years.” Not only is this future possible, but I would bet on it.

Getting from here to there will be a dangerous ride, though. Those vulnerability finders will first be unleashed on existing software, giving attackers hundreds if not thousands of vulnerabilities to exploit in real-world attacks. Sure, defenders can use the same systems, but many of today’s Internet of Things (IoT) systems have no engineering teams to write patches and no ability to download and install patches. The result will be hundreds of vulnerabilities that attackers can find and use.

Posted on April 20, 2020 at 6:22 AMView Comments

Microsoft Buys Corp.com

A few months ago, Brian Krebs told the story of the domain corp.com, and how it is basically a security nightmare:

At issue is a problem known as “namespace collision,” a situation where domain names intended to be used exclusively on an internal company network end up overlapping with domains that can resolve normally on the open Internet.

Windows computers on an internal corporate network validate other things on that network using a Microsoft innovation called Active Directory, which is the umbrella term for a broad range of identity-related services in Windows environments. A core part of the way these things find each other involves a Windows feature called “DNS name devolution,” which is a kind of network shorthand that makes it easier to find other computers or servers without having to specify a full, legitimate domain name for those resources.

For instance, if a company runs an internal network with the name internalnetwork.example.com, and an employee on that network wishes to access a shared drive called “drive1,” there’s no need to type “drive1.internalnetwork.example.com” into Windows Explorer; typing “\\drive1\” alone will suffice, and Windows takes care of the rest.

But things can get far trickier with an internal Windows domain that does not map back to a second-level domain the organization actually owns and controls. And unfortunately, in early versions of Windows that supported Active Directory — Windows 2000 Server, for example — the default or example Active Directory path was given as “corp,” and many companies apparently adopted this setting without modifying it to include a domain they controlled.

Compounding things further, some companies then went on to build (and/or assimilate) vast networks of networks on top of this erroneous setting.

Now, none of this was much of a security concern back in the day when it was impractical for employees to lug their bulky desktop computers and monitors outside of the corporate network. But what happens when an employee working at a company with an Active Directory network path called “corp” takes a company laptop to the local Starbucks?

Chances are good that at least some resources on the employee’s laptop will still try to access that internal “corp” domain. And because of the way DNS name devolution works on Windows, that company laptop online via the Starbucks wireless connection is likely to then seek those same resources at “corp.com.”

In practical terms, this means that whoever controls corp.com can passively intercept private communications from hundreds of thousands of computers that end up being taken outside of a corporate environment which uses this “corp” designation for its Active Directory domain.

Microsoft just bought it, so it wouldn’t fall into the hands of any bad actors:

In a written statement, Microsoft said it acquired the domain to protect its customers.

“To help in keeping systems protected we encourage customers to practice safe security habits when planning for internal domain and network names,” the statement reads. “We released a security advisory in June of 2009 and a security update that helps keep customers safe. In our ongoing commitment to customer security, we also acquired the Corp.com domain.”

Posted on April 9, 2020 at 6:45 AMView Comments

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Sidebar photo of Bruce Schneier by Joe MacInnis.